Direction indicator for automobile

ABSTRACT

A direction indicator for automobiles having a negative grounded battery and utilizing semiconductor circuits for the control of two or more sets of lights individually with the lights of each set being operated in sequence or simultaneously to indicate a change in direction of the vehicle and relatively high resistance lights in series with the direction lights to indicate to the driver improper operation of the circuit.

United States Patent Okuhara 14 Dec. 19,1972

[54] DIRECTION INDICATOR FOR AUTOMOBILE [72] Inventor: Seiichi Okuhara,3-5-7, Yoyogi,

Shibuya-ku, Tokyo, Japan [22] Filed: April 23, 1971 [21] Appl. No.:136,847

[30] Foreign Application Priority Data April 30, 1970 Japan ..45/36322[52] US. Cl. "340/82, 315/210, 340/251 [51] int. Cl. ..B60q 1/38 [58]Field of Search...315/209, 210, 209 SC; 340/82, 340/83 [56] ReferencesCited UNITED STATES PATENTS 3,113,241 12/1963 Yonuehka ....340/83 UX3,376,472 4/1968 Taylor ct al. ..340/83 X 3,391,304 7/1968 Fabry..340/83 X 3,474,410 10/1969 lvec ..340/82 Primary Examiner-Kenneth N.Leimer Attorney-Eugene E. Geoffrey, Jr.

[57] ABSTRACT A direction indicator for automobiles having a negativegrounded battery and utilizing semiconductor circuits-for the control oftwo or more sets of lights individually with the lights of each setbeing operated in sequence or simultaneously to indicate a change indirection of the vehicle and relatively high resistance lights in serieswith the direction lights to indicate to the driver improper operationof the circuit.

1 4 Claims, 3 Drawing Figures TRIGGER GE N.

PATENTED DEC 19 I972 TRIGGER TR IGGER All T GEN.

TR IGGER GE N . INVENTOR. (YE/law 05 5 4 DIRECTION INDICATOR FORAUTOMOBILE This invention relates to a direction indicator forautomobiles, especially to an electronic circuit for operating such adirection indicator, which includes a plurality of laterally arrangedelectric lamps illuminated sequentially one by one from left to right orfrom right to left and all the lamps are simultaneously extinguishedafter the last lamp is illuminated. This operation is then repeated toprovide an indication of the travelling direction of the automobile.

Direction indicators of this type have been already used in someautomobiles. However, these direction indicators according to the priorart have been operated by sequentially switching a train of mechanicalswitch contacts of a lamp circuit by means of an electric motor andnumerous troubles have been encountered such as mis-illumination andimproper illumination of the lamps due to abrasion of the switchcontacts or deterioration of the contact springs.

In order to overcome the difficulties of prior direction indicators, anelectronic switching circuit has been proposed which utilizes electronicswitching elements such as silicon controlled rectifiers (hereinafterreferred to as SCR) in place of the mechanical switches and has overcomethe difficulties caused thereby. However, the circuit presentsdifficulties in that its circuit configuration including the indicationlamps requires that one terminal of each lamp be connected to thepositive terminal of the power supply and the circuit therefore cannotbe applied directly to an automobile of negative-grounded type which isnow most commonly used.

One object of this invention is to provide an improved directionindicator circuit which is directly applicable to the negative-groundedtype automobile.

This object can be attained by providing a circuit comprising aplurality of indication lamps each having one terminal connected to thenegative terminal of the power supply in accordance with this invention.In the circuit of this invention, (n 1) series connections eachconsisting of an SCR and a lamp connected to the cathode electrodethereof and included in the first through (n 1)th stages of the circuit,and one series connection consisting of an SCR and a resistor connectedto the cathode electrode thereof and included in the n-th stage of thecircuit are connected in parallel between the positive and negativeterminals of the d.c. source. A commutating capacitor is connectedbetween the cathode electrode of the SCR in the first stage and thecathode electrode of the SCR in the n-th stage, and circuitsrespectively including a capacitor and an impedance element areconnected respectively between the cathode electrodes of the SCRs in thesecond through (n l)th stages and the cathode electrode of the SCR inthe n-th stage. The impedance element is selected to have an impedancevarying in accordance with the direction of the current passingtherethrough.

Other objects and features of this invention will be best understoodfrom the following description with reference to the accompanyingdrawings.

In the drawings:

FIG. 1 is a circuit diagram of one embodiment of a direction indicatorcircuit according to this invention;

FIG. 2 is a circuit diagram of a modification of the circuit of FIG. 1;and

FIG. 3 is a circuit diagram is still another modification of the circuitof FIG. 1.

Throughout the drawings, like reference numerals are used to denote likecircuit elements.

Referring now to FIG. 1, the circuit consists of four stagesrespectively including three lamps 21, 22, and 23 and a resistor 24. Thelamps 21, 22, and 23 are to be attached to the tail of the automobileand controlled by the circuit of this invention for indicating thetravelling direction of the automobile. One end of each lamp 21, 22 and23 and the resistor 24 are respectively connected to the cathodeelectrodes of four SCRs 11, 12, 13, and I4, and the other ends thereofare connected in common to the negative terminal 4 of the dc. source 1.The anode electrodes of the SCRs ll, 12, 13, and 14 are connected incommon to the positive terminal of the dc. source 1 through a switch 2.

The gate electrode of the SCR 11 in the first stage is connected througha series connection of a capacitor 41 and two resistors 91 and 51 to thepositive terminal of the source 1, the gate electrode of the SCR 12 inthe second stage is connected through a series connection of a capacitor42 and two resistors 92 and 52 to the cathode electrode of the SCR 11 inthe first stage, the gate electrode of the SCR 13 in the third stage isconnected through a series connection of a capacitor 43 and tworesistors 93 and 53 to the cathode electrode of the SCR 12 in the secondstage, and the gate electrode of the SCR 14 in the fourth stage isconnected through a series connection of a capacitor 44 and tworesistors 94 and 54 to the cathode electrode of the SCR 13 in the thirdstage.

The junctions of the capacitor 41 and resistor 91, the capacitor 42 andresistor 92, the capacitor 43 and the resistor 93 and the capacitor 44and resistor 94 are respectively connected through diodes 31, 32, 33,and 34 to the output terminal 5 of a trigger pulse generator 3, and thejunctions of the both resistors 91 and 51, etc., in the respectivestages are connected respectively through capacitors 101, 102, 103, and104 to the negative terminal 4 of the source 1. The combinations of theresistor 51 and capacitor 101, the resistor 52 and capacitor 102, theresistor 53 and capacitor 103 and the resistor 54 and capacitor 104respectively constitute filter circuits. The input terminal of thetrigger pulse generator 3 is connected to the positive terminal of thesource 1.

The cathode electrode of the SCR 11 in the first stage is also connectedthrough a capacitor 61 to the cathode electrode of the SCR 14 in thefourth stage. The cathode electrodes of the SCRs 12 and 13 in the secondand third stages are respectively connected through a series connectionconsisting of a capacitor 62 and a parallel connection of a diode 72 anda resistor 82 and a series connection consisting of a capacitor 63 and aparallel connection of a diode 73 and a resistor 83 to the cathodeelectrode of the SCR 14. The SCRs 11, 12, 13 and 14 have respectivelygate leakage resistors 111, 112, 113, and 114 connected between thecathode and gate electrodes thereof.

In operation, the switch 2 is closed to apply an operating voltage fromthe d. c. source 1 to the respective series connections of the SCRs 11,12, 13, and 14 and the lamps 21, 22, and 23 and the resistor 24 and alsostart the operation of the trigger pulse generator 3.

At first, all of the SCRs 11, 12, 13, and 14 are nonconductiveandtherefore the cathode electrodes of the SCRs are at a same potentialas that of the negative terminal 4 of the source 1. Accordingly, nocurrent flows through the diodes 32, 33 and 34 in the second throughfourth stages, while a current flows through the diode 31 in the firststage and through the resistors 91 and 51 and the pulse generator 3.

I When a positive trigger pulse is generated from the trigger pulsegenerator 3 in the above condition, it cancels the current in the diode31 for the duration of the pulse and therefore, raises the potential atthe junction of the resistor 91 and the diode 31, thereby transferringthe trigger pulse through the capacitor 41 to the gate electrode of theSCR 11 in the first stage. The first trigger pulse drives the SCR 11into conduction and illuminates the lamp 21. Due to the conduction ofthe SCR 11, its cathode potential is raised substantially to the voltageof the source 1. Therefore, a part of the conduction current is filteredby the filter circuit consisting of the resistor 52 and capacitor 102and flows through the resistor 92 and the diode 32, thereby maintainingthe junction of the capacitor 42 and the diode 32 at low potential.

The second positive trigger pulse appearing at the output terminal 5 ofthe pulse generator 3 in the above the diode 32 and therefore raises thepotential at the junction of the diode 32 and the resistor 92 for theduration of the pulse thereby transferring the second trigger pulsethrough the capacitor 42 to the gate electrode of the SCR 12 in thesecond stage. Thus, the SCR 12 is driven into conduction to illuminatethe lamp 22.

In the same manner, the SCR 13 in the third stage is driven intoconduction and the lamp 23 is illuminated by the third trigger pulse.Thus, thecathode potentials of the SCRs 12 and 13 in the second andthird stages are substantially raised to the voltage of the source 1 andtherefore the commutating capacitors 62 and 63 connected to the cathodeelectrodes of these SCRs are charged relatively slowly through theresistors 82 and 83 respectively. The commutating capacitor 61 connectedto the cathode electrode of the SCR 11 in the first stage is alsocharged through the resistor 24.

When the fourth trigger pulse appears, it drives the SCR 14in the fourthstage into conduction in the same manner as in the case of the SCR 13,and the cathode potential of the SCR 14 is raised substantially to thevoltageof the source 1. Therefore, the charges stored in the commutatingcapacitors 61, 62 and 63 are concurrently discharged and raise thecathode potentials of the SCRs 11, 12, and 13 above the anode potentialsthereof for a predetermined period and cause the SCRs 11, 12, and 13 tobecome nonconducting and extinguish all of the lamps 21, 22, and 23.Thus the circuit is restored to its original condition except for theSCR 14in the last stage.

* The SCR 14 is retained in the conduction mode and the cathodepotential thereof is nearly equal to the source voltage. Therefore, thecommutating capacitor 61 is charged inversely to the above case so thatone electrode connected to the cathode electrode of the SCR 14 is poledpositive and the other electrode connected to the cathode electrode ofthe SCR 11 is poled negative. When the next trigger pulse appears withthe circuit in this condition, it drives the SCR 1 1 in the first stageinto conduction to illuminate the lamp 21 and discharge the commutatingcapacitor 61, thereby raising the cathode potential of the SCR 14 abovethe anode potential thereof and disables the SCR 14.

By repeating the above mentioned'operation, the sequential illuminationand simultaneous turning off of the lamps 21 22 and 23 is periodicallyrepeated, thereby indicating the travelling direction from left toright, for example.

The diode 72 serves the function of preventing the commutating capacitor62 from being charged quickly and causing it to be charged slowlythrough the resistor- 82 when the SCR 12 is driven into conduction.Similarly, the diode73 servesthe function of preventing the commutatingcapacitor 63 from being charged quickly and causing it to be chargedslowly through the resistor 83 when the SCR 13 is driven intoconduction. However, when the SCR 14 in the last stage is driven intoconduction and raises its cathode potential, the three commutatingcapacitors 61, 62, and 6.3 are concurrently discharged. Thus thecapacitors 62 and 63 are charged only through the resistors 82 and 83and discharged only through the diodes 72 and 73, respectively.Therefore, it is necessary to provide a charging time for the capacitors62 and 63 sufficiently longer than the discharging time thereof and thevalues of the resistors 82 and 83 are therefore relatively large.

If the diodes 72 and 73 were not inserted, only one SCR could conduct ata time. In other words, for example, if the SCR 12 is driven intoconduction following the SCR 11, the cathode potential of the SCR 11 israised for a short time as a result of the discharge of the capacitor 61and thereby the SCR 11 is disabled. Therefore, the lamps will beindividually illuminated one by one, as in the case of a ring counteroperation,

and it would be impossible to illuminate a plurality of lamps at thesame time. As described above,-the circuit including the diodes 72 and73 serves the function of illuminating a plurality of lamps at the sametime and also serves the function of concurrently turning off the alllamps.

Referring next to FIG. 2 representing a first modification of thecircuit of FIG. 1, except single-pole double-throw switches 6 and 7 arerespectively inserted between the SCR 11 and the resistor 52 and betweenthe SCR 12 and the resistor 53. In the both switches, the movablecontact is connected to the resistor and two fixed contacts arerespectively connected to the anode and cathode electrodes of the SCR.The movable contacts of the both switches are preferably interlocked.

When the movable contacts of the switches 6 and 7 are connected to thecathodes of the SCRs 11 and 12, the circuit operation is identical tothat of the circuit of FIG. 1. However, when the movable contacts areswitched to the anode side (opposite side in the drawing), this circuitoperates as follows.

While none of the SCRs conducts at first, current flows in the diodes31, 32, and 33- through the series connection of the resistors 51 and91, the series connection of the resistors 52 and 92 and the seriesconnection of the resistors 53 and 93, respectively. The first triggerpulse supplied from the trigger pulse generator 3 under these conditionscancels the current in the diodes 31 and 32 and 33 for the durationthereof and raises the potentials at the junction of the resistor 91 andthe diode 31, the junction of the resistor 92 and the diode 32 and thejunction of the resistor 93 and the diode 33. These raised potentialsare respectively transferred through the capacitors 41, 42 and 43 to thegate electrodes of the SCRs 11, 12, and 13 and drive these SCRs intoconduction at the same time, thereby illuminating the lamps 21, 22, and23 concurrently.

At this time, the cathode potential of the SCR 13 rises and a currentflows in the diode 34 through the resistor 54 and 94. The second triggerpulse then supplied cancels the current in the diode 34 and raises thepotential at the junction of the resistor 94 and the diode 34. Thispotential is transferred through the capacitor 44 to the gate electrodeof the SCR 14-and drives it into conduction. Thereby, the cathodepotential of the SCR 14 is raised and therefore the commutatingcapacitors 61, 62, and 63 are discharged concurrently to raise thecathode potentials of the SCRs 11, 12, and 13 for a short time renderingthese SCRsll, 12, and 13-nonconductive and extinguishing all of thelamps 21, 22, and 23 at the same time.

When the third trigger pulse is supplied, the SCRs 11, 12 and 13 areagain driven into conduction to illuminate the lamps 21, 22, and 23 atthe same time, and the commutating capacitor 61 is charged to render theSCR 14 nonconductive.

By repeating the abovementioned operation, the lamps 21, 22 and 23 areconcurrently and cyclicly illuminated and extinguished. It is noted thatthe group of three SCRs l1, l2, and 13 and the SCR 14 cooperate to forma circuit similar to a flip-flop circuit. Thus this circuit can be usedfor indicating emergency parking of the automobile.

The circuit of FIG. 3 is a second modification of the circuit of FIG. 1and is similar to'it, except that the junctions of the resistors 52 and92 and the resistors 53 and 93 are connected through respective diodes122 and 123 and a common single-pole single-throw switch 8 to thepositive electrode of the dc source 1. It will be readily understoodthat this circuit operates in the same manner as the circuit of FIG. 2when the switch 8 is closed.

' In the above embodiments, if it is assumed that the lamps 21, 22 and23 are used for indicating a right turn of the automobile, it isnecessary to change connections to the lamps 21, 22 and 23 to anotherset of three lamps (not shown) for a left turn. This can be accomplishedby inserting a relay or change-over switch in the cathode side of eachSCR.

A further modification of the circuit may include an indicating lamp 130having a high internal resistance and relatively low power consumptionand connected between the anode and cathode electrodes of each of theSCRs 11, 12, and 13. These indicating lamps may be arranged on the meterpanel for the operator in the automobile to confirm the operation of thelamps 21, 22 and 23 and indicate malfunctions relating to the lamps,such as broken filaments, disconnections and improper contacts.

In the above mentioned embodiments, the resistor 24 can be replaced by alamp which is disposed on the front or side of the automobile, thoughthe time of illumination is short and the tirnejt is extinguished islong.

Since in the circuit of this invention one terminal of each lamp isconnected directly to the negative terminal of the source, the circuitcan be conveniently installed in automobiles of negative-grounded type.

What is claimed is:

1. A direction indicator for an automobile comprising a first circuithaving first through n-th stages, a dc. source for supplying anoperating voltage to said stages, a pulse generator for generating atrain of trigger pulses, each of said first through (n-l )th stagesincluding a series connection of a silicon controlled rectifier and adirection indicating lamp forwardly connected between the both terminalsof said d.c. source, and said n-th stage including a series connectionof a silicon controlled rectifier and a resistor forwardly connectedbetween both terminals of the dc. source, said lamps and said resistorbeing connected respectively to the cathode electrodes of said siliconcontrolled rectifiers, a commutating capacitor connected between thecathode electrode of the silicon controlled rectifier in the first stageand the cathode electrode of the silicon controlled rectifier in then-th stage, a series connection of a capacitor and an impedance elementconnected between the cathode electrode of the silicon controlledrectifier in each of the second through (nl)th stages and the cathodeelectrode of the silicon controlled rectifier in the nth stage, saidimpedance element having an impedance varying in accordance with thedirection of current passing therethrough, and second circuit means forapplying said trigger pulses sequentially to the gate electrodes of saidsilicon controlled rectifiers in the first through n-th stages.

2. A direction indicator for an automobile, according to claim 1 whereinsaid impedance element consists of a parallel connection of a diode anda resistor.

3. A direction indicator for an automobile according to claim 1including third circuit means for applying said trigger pulsesconcurrently to the gate electrodes of said silicon controlledrectifiers in the first through (n 1)th stages, and switch means forselectively interchanging said second circuit means and said thirdcircuit means.

4. A direction indicator for an automobile according to claim 1 whereineach of said first through (n l)th stages includes an operationindicating lamp connected between the anode and cathode electrodes ofthe silicon controlled rectifier in that stage, said operationindicating lamp having alower power consumption than the directionindicating lamp in that stage.

Q t I

1. A direction indicator for an automobile comprising a first circuithaving first through n-th stages, a d.c. source for supplying anoperating voltage to said stages, a pulse generator for generating atrain of trigger pulses, each of said first through (n-1)th stagesincluding a series connection of a silicon controlled rectifier and adirection indicating lamp forwardly connected between the both terminalsof said d.c. source, and said n-th stage including a series connectionof a silicon controlled rectifier and a resistor forwardly connectedbetween both terminals of the d.c. source, said lamps and said resistorbeing connected respectively to the cathode electrodes of said siliconcontrolled rectifiers, a commutating capacitor connected between thecathode electrode of the silicon controlled rectifier in the first stageand the cathode electrode of the silicon controlled rectifier in then-th stage, a series connection of a capacitor and an impedance elementconnected between the cathode electrode of the silicon controlledrectifier in each of the second through (n-1)th stages and the cathodeelectrode of the silicon controlled rectifier in the nth stage, saidimpedance element having an impedance varying in accordance with thedirection of current passing therethrough, and second circuit means forapplying said trigger pulses sequentially to the gate electrodes of saidsilicon controlled rectifiers in the first through n-th stages.
 2. Adirection indicator for an automobile, according to claim 1 wherein saidimpedance element consists of a parallel connection of a diode and aresistor.
 3. A direction indicator for an automobile aCcording to claim1 including third circuit means for applying said trigger pulsesconcurrently to the gate electrodes of said silicon controlledrectifiers in the first through (n - 1)th stages, and switch means forselectively interchanging said second circuit means and said thirdcircuit means.
 4. A direction indicator for an automobile according toclaim 1 wherein each of said first through (n - 1)th stages includes anoperation indicating lamp connected between the anode and cathodeelectrodes of the silicon controlled rectifier in that stage, saidoperation indicating lamp having a lower power consumption than thedirection indicating lamp in that stage.